1. Field of the Invention:
This invention relates to an apparatus for boring a hole affording communication between a first member such as a tubular member and a plate-like member and a second tubular or annular member connected to the first member and, more particularly, to an apparatus for boring a hole, which affords communication between a first pipe like a main pipe of sewerage and a second pipe like a mounting pipe or branch pipe connected to the first pipe, from the side of the first pipe.
2. Description of the Prior Art:
Various methods for disposing new pipes in existing pipes such as sewer pipes, water-supply pipes, gas pipes, pipes for power line and pipes for telephone line and for applying coating or lining to the inner surface of an existing pipe have been proposed and executed in order to reproduce the existing pipes. According to these reproducing methods, newly installed pipes are provided in the interior of the existing pipe to be substantially integral therewith. However, since the reproduced pipe in accordance with these methods has a problem that a pipe opening of a branch pipe is closed with the newly installed pipe, it is necessary to bore a hole for opening the pipe opening of a branch communicating to the existing pipe to the interior of the reproduced pipe.
As for one of apparatuses for boring such hole, there has been proposed an apparatus for boring a hole in a newly installed pipe from the interior of a reproduced pipe with a cutter rotated about the axis extending in the radial direction of the pipe to cut away a portion of the pipe (for example, Japanese Utility Model Public Disclosure (KOKAI) No. Sho 61-35370). This boring apparatus bores a hole in the newly installed pipe by rotating the cutter about the axis extending in the radial direction of the reproduced pipe while shifting the cutter outwardly in the radial direction after the boring apparatus is determined in position inside the reproduced pipe so that the cutter is opposed to the pipe opening of the branch pipe.
However, in the prior boring apparatus, use is made of a conical cutter having the maximum diameter larger than that of a hole to be bored and the cutter is maintained in position to be immovable relative to the first pipe during the boring operation. Therefore, the boring apparatus has to be determined in position so that a rotary axis of the cutter coincides with the center of the pipe opening of the branch pipe. Unless the boring apparatus is determined in position in such way, there is a possibility of cutting away the branch pipe portion or a predetermined hole in size cannot be bored.